| The purpose of the study is to explore the mechanisms,approaches,and key technologies for the efficient utilization of super-rice nitrogen fertilizers,and then to establish a high-efficiency utilization technology system for super-rice nitrogen nutrient,to achieve high-efficiency,low-consumption,and environmental sustainability of super rice production.In the early and late seasons of 2017,four super-rice varieties such as Zhongjiazao17,Zhuliangyou819,Tianyouhuazhan,and Hyou 518 were used as materials,and urea,slow-release urea,ammonium sulfate,and potassium nitrate were selected in experiment conducted in Mei Hua village,Xi Du Town,Hengyang County,so as to explore the effects of different fertilizer forms on the N use efficiency of super-rice.The main results were as follows:(1)The rice yields of ZhongJiaZao17,ZhuLiangYou819,Tianyouhuazhan,and Hyou 518 all reached the maximum under urea treatment,higher than other treatments 6.35%-96.87%,0.99%-80.89%,7.14%-53.84%,3.20%-54.03%,respectively.The difference between the urea treatment of the late rice variety Tianyouhuazhan and other treatments was significant.The other three varieties,the difference between urea treatment and other three treatments(ammonium sulfate treatment,potassium nitrate treatment and no fertilizer treatment)was significant.It indicates that amide nitrogen is more suitable for super rice,and ammonium nitrogen is better than nitrate nitrogen for super rice.Urea treatment increased the number of productive panicles and grains per panicle.The highest seed setting rate was achieved with no nitrogen treatment and ammonium sulfate treatment.There was a significant positive correlation between the yield of rice and the number of productive panicles and grains per panicle.(2)The leaf area index of rice reached the maximum at the full heading stage,and the one under urea treatment was the highest at the mature period,followed by the slow-release urea treatment.Nitrogen form is an important factor affecting the accumulation of dry matter.There was a significant positive correlation between leaf area index and dry matter and yield at the late growth stage of rice.The material output and material conversion rate of shoot apex and leaf,as well as dry matter accumulation after heading were the highest in urea treatment,and had a significant positive correlation with yield.Root activity was the highest with urea treatment and slow-release urea treatment,and was significantly positively correlated with yield.(3)The SPAD value is influenced by the nitrogen form significantly.Both ZhongJiaZao17 and ZhuLiangYou819 had the highest SPAD value in urea treatment,while the late rice was in ammonium sulfate treatment,and was positively correlated with yield.The photosynthetic characteristics of rice were affected by nitrogen significantly.The net photosynthetic rate and stomatal conductance of four varieties were all highest in urea treatment;rice yield was positively correlated with transpiration rate and net photosynthetic rate,and no significant correlation with intercellular CO2 concentration and stomatal conductance.(4)The nitrogen content in all organs of rice was the highest in urea treatment.The effects of nitrogen fertilizer forms on nitrogen utilization rates are in the following order: nitrogen absorption and utilization rate > soil dependency rate > nitrogen utilization rate > nitrogen contribution rate > agronomic utilization > nitrogen fertilizer partial productivity.Nitrogen fertilizer partial productivity,nitrogen contribution rate,agronomic efficiency and nitrogen absorption rate were the highest in urea treatment,positively correlated with yield.The physiological utilization rate of nitrogen and the rate of soil nitrogen dependence were highest in potassium nitrate treatment,negatively correlated with yield.Therefore,in the process of super rice production,the first choice is amide nitrogen fertilizer,followed by slow-release amide nitrogen fertilizer for increasing production and fertilizer utilization rate. |
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